Manufacture of highly polymeric poly-



2,899,410 Patented Aug. 1 1, 1959 MANUFACTURE OF HIGHLY POLYMERIC -'PoLY- METHYLENE TEREPHTHALATES of said copolyesters is present to an extent of at least 89 moles percent but'not more than 95 moles percent.

Examples of the functional derivatives of terephthalic acid which may be used are half esters, esters including cycle-aliphatic esters and aryl esters ester halides and Norman Standrmg Harrogate England asslgnor to Imk perial Chemical industries I Jimited, Ifondon, England, ammpmum. or amme salts In the preferred process of a corporation of Great Britain our invention we react ethylene glycol and 1:4 butane diol with dimethyl terephthalate. No Drawing. Appllcauon September 24, 1956 If the copolyester is required in a delustred form, a Serial 611,744 small amount, e.g. 0.5% of titanium dioxide may be Claims priority, application Great Britain October 7, .1955 added to the reaction mixture. Any suitable ester-interchange and/or polycondensatlon catalyst may be used in 2 Clfilmsthe copolyester forming reaction and we have found litharge and zinc oxide especially suitable for this pur- This mvention relates to the manufacture of highly 5 se. polymeric polymcthylene terephthalates, more particular The following table gives examples illustrating the proc- Y to a 1 3 2 f ethylene y 114 butane (1101 ess of our invention but does not limit the scope thereof, and terephthalic acld. 1 together with a comparative example.

Composition Polycondensation Time Ester Interchange Soften- Polycon- Time Less than ing densation Example Ethylene 1:4 Total 1mm.pres- Point, Temp.,

Glycol, Butane sure 0. 0. M perd101, M

cent percent hr. min. hr. min. hr. min.

Comparative 100 4 2 1 26 260 275 Polyethylene terephthalate and polytetramethylene ter- In each example in the table are used 250 molar parts ephthalate are polyesters suitable for the manufacture of of the mixture of ethylene glycol and 1:4 butane diol in fibre and film-forming materials, having softening points the proportions stated. These substances are heated for of 260 C. and 230 C. respectively. the time stated, the temperature rising through the range We have now found that by copolymerising ethylene 150-2l5 C., with 100 molar parts of dimethyl terephglycol terephthalate with tetramethylene glycol terephthalate containing 0.15 part by weight of litharge as catathalate, the process may be carried out at lower temperalyst. The mixture so formed is polycondensed under the tures which permit the use of large quantities of catalyst conditions tabulated to give copolyesters of softening in the copolyester forming reaction, giving faster reaction points stated therein. times. If the diol reaction charges from which these 45 All the copolyesters so obtained are of suitable colour copolyesters are to be formed contain at least 89 moles and viscosity for the manufacture of drawable fibres and percent of ethylene glycol but not more than 95 moles films. percent, the resulting copolyesters have melting points be- The comparative example is similarly undertaken but tween that of polyethylene terephthalate and polytetra- 50 using 0.015 part by weight of zinc acetate and 0.02 part methylene terephthalate and have excellent fibre and film by weight of antimony oxide as the catalyst system. forming properties. The softening point of the copolyesters and that of More specifically the softening points of these cothe polyethylene terephthalate containing not more than polyesters lie in the range 230-245 C. and can there- 35% 1:4 butane diol, i.e. those obtained by the process fore be melt polycondensed at low temperatures e.g. 250 of our invention is given by the equation, C Much higher catalyst concentrations can therefore be Softening point C.=258.7 used than 1s posslble 111 the melt polycondensation of 77Xmoles percent butane diol polyethylene terephthalate, resulting in reduced cycle times without the accompanying disadvantages such as Where the softemng point of the polymer is the temperahigh rate of discolouration. 6O ture at which a plunger weight 29.5 grams, circular cross According to the present invention we provide a process for the manufacture of a copolyester from ethylene glycol, 1:4 butane diol and terephthalic acid, or functional derivatives thereof, wherein the ethylene glycol in the diol charge of the reaction mixture for the formation section, A diameter sinks 0.02 into the precrystallised polymer. The term moles percent butane diol refers to the initial composition of the mixed glycols.

The table thus shows that lower polycondensation temperatures can be employed, permitting the use of high catalyst concentrations with consequent improvement in cycle times, particularly ester-interchange time as compared with the conditions required for the formation of polyesters from ethylene glycol alone.

Filaments and fibres obtained from the copolyesters which are the subject of the present invention exhibit increased dye uptake over the homopolyester, polyethylene terephthalate.

What we claim is:

l. A process for the manufacture of dyeable fiberand film-forming copolyesters of polymethylene terephthalate having a softening point between about 230 and 240 C., which comprises reacting a glycol mixture containing between 89 and 95 mol percent of ethylene glycol and between 11 and 5 mol percent of tetramethylene glycol 4 with dimethyl terephthalate, under heating at a temperature between ISO-215 C. to bring about ester-interchange, followed by heating under polycondensation conditions at a temperature of substantially about 250 C. and in the presence of litharge as an ester-interchange and polycondensation catalyst.

2. Copolyesters of ethylene glycol and tetramethylene glycol and terephthalic acid produced by the process according to claim 1.

Whinfield Mar. 22, 1949 Izard Dec. 12, 1950 

1. A PROCESS FOR THE MANUFACTURE OF DYEABLE FIBER-AND FILM-FORMING COPOLYESTERS OF POLYMETHYLENE TEREPHTHALATE HAVING A SOFTENING POINT BETWEEN ABOUT 230* AND 240*C., WHICH COMPRISES REACTING A GLYCOL MIXTURE CONTAINING BETWEEN 89 AND 95 MOL PERCENT OF ETHYLENE GLYCOL AND BETWEEN 11 AND 5 MOL PERCENT OF TETRAMETHYLENE GLYCOL AND WITH DIMETHYL TEREPHALATE, UNDER HEATING AT A TEMPERATURE BETWEEN 150-215*C. TO BRING ABOUT ESTER-INTERCHANGE, FOLLOWED BY HEATING UNDER POLYCONDENSATION CONDITIONS AT A TEMPERATURE OF SUBSTANTIALLY ABOUT 250*C. AND IN THE PRESENCE OF LITHARGE AS AN ESTER-INTERCHANGE AND POLYCONDENSATION CATALYST. 